1. Technical Field
This invention relates in general to integrated circuits and, more particularly, to managing energy in a processor.
2. Description of the Related Art
For many years, the focus of processor design, including designs for microprocessor units (MPUs), co-processors and digital signal processors (DSPs), has been to increase the speed and functionality of the processor. Presently, energy consumption has become a serious issue. Importantly, maintaining low energy consumption, without seriously impairing speed and functionality, has moved to the forefront in many designs. Energy consumption has become important in many applications because many systems, such as smart phones, cellular phones, PDAs (personal digital assistants), and handheld computers operate from a relatively small battery. It is desirable to maximize the battery life in these systems, since it is inconvenient to recharge the batteries after short intervals.
Currently, approaches to minimizing energy consumption involve static energy management; i.e., designing circuits which use less energy. In some cases, dynamic actions have been taken, such as reducing clock speeds or disabling circuitry during idle periods.
While these changes have been important, it is necessary to continuously improve energy management, especially in systems where size and, hence, battery size, is important to the convenience of using a device.
In addition to overall energy savings, in a complex processing environment, the ability to dissipate heat from the integrated circuit becomes a factor. An integrated circuit will be designed to dissipate a certain amount of heat. If tasks (application processes) require multiple systems on the integrated circuit to draw high levels of current, it is possible that the circuit will overheat, causing system failure or errant behavior.
In the future, applications executed by integrated circuits will be more complex and will likely involve multiprocessing by multiple processors, including MPUs, DSPs, coprocessors and DMA channels in a single integrated circuit (hereinafter, a “multiprocessor system”). DSPs will evolve to support multiple, concurrent applications, some of which will not be dedicated to a specific DSP platform, but will be loaded from a global network such as the Internet. This is especially true in wireless multimedia appliances domain, where severe cost constraints require the use of a small, low pin count, low cost, packaging technology. Accordingly, the tasks that a multiprocessor system will be able to handle without overheating will become uncertain.
Accordingly, a need has arisen for a method and apparatus for managing energy in a circuit without seriously impacting performance.